Glass



April 20, 1954 R. B. BARNES ETAL 2,676,109

GLASS Filed Dec. 22, 1950 5 Sheets-Sheet l 4 INVE NT OKS n 4 ,2 3 RQBEKT Bowuus BARNES WALTER A- F'RASE-R wzodo jdi Z. FEZMJMZQ; 3 3 Q2. 3 8 3 3 8m 8 3 3 3 8m 3 3 3 3 8+ R. B. BARNES ETAL- GLASS 5 Sheets-Sheet 2 April 20, 1954 Filed Dec. 22, 1950 fluvaazad) norssvwswvzu;

, INVENTORS ROBERT Bowuus 3ARNE$ WALTER A- FRASE- BY ATTORNEY April 20, 1954 R. B. BARNES EII'AL 2,676,109

ROBERT BOWLlNG BARNES WALTER A- FKA$ER ATTORN Y April 20, 1954 R. B. BARNES ET AL GLASS Filed Dec. 22, 1950 N ww 5 Sheets-Sheet 4 BSNVLLNNSNVHJ- (.maoaaa) INVE NTORS MA w N m a M April 20, 1954 Filed Dec/22, 1950 BARNES ETAL 5 Sheets-Sheet 5 ATTORNEY Patented Apr. 20, 1954 .GLAS S RibliertBoWling -Barnes, Stamford, and Walterii. Frasen Ridgefield, Conn.',- assignors to Anieri Bean I Optical Company, -So'uthbridge, Mass'.,-' a *voluntaryassociation of Massachusetts Amilication December 22, mimsermrNo. 202378 NI TED PATENT FI CE '14 Claims.

-mventronr1stes "to improvements in glasses havin'g"controlledabsorptive characteristics as to visible and invisible portions of the spectrum and further including other-injurious rays; and has particular-reference to 'novelcompositions and- -method ofmaking the same.

as a result of the-bombardment of thefluorescent "coating' of said screen by'an electronbeam.

Among the various dificulties-which have: been encountered, the following seem to be the tmost troublesome:

A. The provision of'good discrimination Shetween grays and-blacks in the image and, there- Lfore, desirable contrast. B. Elimination of diffusion introducedhy'halations resulting from reflectionsof the light emanating from the fluorescing particles of the screen ofthe tube.

*CfiThe altering- =ofthe visible ray transmission to obtain a morepraetlcallevel of transmission' -for introducing greater visual'comfort -Without: substantially orrperceptibly- .affectingzthercolor ofrthetimage.

.The maintenance of the'threshold of-vision of observers at substantially the normal :levels. E. .illiminationvoi harmtul X-rayv radiation. LF', -EJliriai'nation ofl reflections fromsources outside thetube. 'Gflnithe casefoiacathode ray tube'having a metallic envelopeiand1a glass facefthe control- -a principal sweet ofthe iiresent invention *to discrimination ing and us'in'g'the same 'tthrhy substantially all or the above 'difii'culti's are greatly reduced.

"'Anothervfobject'is to provide "a la'ssicomposition suit'ab'lef'or"use in forming thefae'g portion of a. cathode "raytiitie orjin i'forming"fi1ters for use with sucl rtu l' es;' andtlfi'ethod of makingfand "using the same whereby. theiabove fdifliculties" are 'greatly reducedorifeliminated. 4

Another o'bjtt"is to provide 'a";lass of '1 the above nature having. its transmission'characteristics" controlledsoi as 'tofierideithevisible1i0r- "sorp'tion o f ult'ra y rays tofth'e eXtent' that 15 "a substantially normal threshold of vision is for "use "in tn,

maintained.

above character {having '-"c'or'itrol1 d *absorfitive 'eharacteristicswith respect to "generated in the'cajthode raytube. u v

Anotherotijetztis tof'provide a"cathoderaytnbe -face-or filterioi l'a-sso'f thy-above character havmg a. "lefiiil n reductic'iricoating on the" outer "surface"thereof'forreducingrefiectionofexternal light andjfor absorbingthe refiection-or internal Another object is to providea cathode ray tube .nate'd structure in which one of thelaminaeisof i a .glass formed ni'n Li -accordance with sth'is I inven- I tion Anothersobjectaiszto .'so;c0ntrol thecoefficients of expansion-def :,-:the wa-rious :1 glasses .iormed in :accordancetwithzthe :present invention whereby they will, more; readily -mateh wthe coeficients of .expansionsofsthe envelppestof the tubessformed of metal tothereby enablethemtoibe readily-and permanently .f fused .witna d.;meta1js.

. Anotherjo jectis'tojp'rovidela, cathode rayltube I "s'ion hav "g its Trace ,lpbrtion formed offgl'dss fjflili'abovell'ietrafiterfWithsaid face *portion having a "transparent coating on '11 Wn chthewoating the outer surface thereof and embodying additional means for eifectively eliminating the internal light reflected from the face of the tube at angles greater than the critical angle.

Other objects and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawings in which:

Fig. l is a side elevational view, partially in section, of a television tube illustrating an embodiment of the invention;

Fig. 2 is an enlarged fragmentary sectional View diagrammatically illustrating the effects of the glass embodying the invention as to one of its uses;

Fig. 3 is a fragmentary sectional view of a cathode ray tube embodying a modification of the invention;

Fig. 4 is a fragmentary sectional view of a filter made in accordance with the present invention;

Figs. 5, 6 and 7 are charts illustrating the spectral transmission curves of several glasses embodying the invention; and

Fig. 8 is a chromaticity diagram diagrammatically illustrating the colors of the glasses referred to in Fig. 5.

Referring more particularly to the drawings wherein like characters of reference designate like parts throughout the views, in Fig. 1 there is illustrated a conventional type television cathode ray tube or kinescope having a face portion 3 formed of glass embodying the invention, cone-shaped side walls i, and a neck portion having a conventional electron gun (not shown) mounted therein and disposed so as to expel a beam of electrons toward said face portion. The cone-shaped walls 4 may be form-ed of glass, metal, or other desirable material in the conventional manner with the glass face portion 3 being secured in sealed relation thereto.

The face portion 3 formed of the glass embodying the invention has a fluorescent screen 7 formed either directly on the inner surface thereof or on a coating 8 of transparent material disposed on the inner surface of the glass. In the latter instance, the transparent coating 8 is adapted to space the screen 7 from the inner surface of the face portion 3 and the function thereof will be described in detail hereinafter. A reflection reduction coating 6 may be formed on the outer surface of the face portion of the tube.

It has been described above that the conical wall portions 4 may be formed of glass. In such instances, however, the glass of said wall portions may be those which are now in common commercial use and need not be of the glass embodying the invention.

It is particularly pointed out that in instances when the cone-shaped walls 4 of the tube are formed of metal, the glass of the face portion 3 is controlled as to its coefficient of expansion so as to closely approach the coefiicient of expansion of the metal of said cone-shaped walls 4, whereby the face-portion 3 may be readily fused to said cone-shaped walls and due to the similarity of said coeflicients of expansion will remain in more permanently sealed relation therewith.

Indealing with the various difiiculties set forth above, the glass embodying the invention preferably has the following characteristics:

1. Transmission in the visible portion of the spectrum ranging approximately from 45% to 70% at 400 millimicrons, 58% to 76% at 500 millimicrons, 50% to 71% at 600 millimicrons, and

4 67% to 80% at 700 millimicrons, and with an average white of from 60% to 75%.

2. Transmission in the ultra-violet portion of the spectrum of approximately from 2% to 31% at 370 millimicrons, approximately from 0 to 13% at 360 millimicrons, approximately from 0% to 3.5% at 350 millimicrons, and with substantially no transmission below 350 millimicrons.

3. Absorption in the X-ray portion of the spectrum of substantially all X-rays generated thereby.

These transmission and absorption values apply to glasses embodying the invention when produced and measured in thicknesses of from 5 to 6 millimeters. However, in certain instances it may be permissible to vary the above specifications in accordance with the results desired and the thickness of the article.

According to the teachings of this invention, an alkali-lime-silica base glass will have added thereto controlled amounts of lead oxide for introducing X-ray absorption, copper oxide and either vanadium Or cerium oxide or mixtures thereof to introduce ultra-violet absorbing characteristics, and cobalt, manganese, or nickel oxide or their mixtures for obtaining the required color. Oxides of silver and titanium may be also added to control the ultra-violet transmission characteristics of the resultant glass. The alkali in the above-mentioned base glass is preferably a mixture of potassium and sodium oxides. Inclusion of boric oxide will also aid in the melting, making the glass more fluid and improving the chemical durability.

The following table lists the ingredients which may be used in producing a batch which when melted in the manner to be described hereinafter will result in a crown glass having desired characteristics:

. n Ingredients gai Silica (SiOz) 60-72 go5ic8ide0B O 0-7 Potash K2o) Lime (CaO) Lead oxide (PbO).. 9-11 Titania ('liOz) 05.0.. Vanadium oxide (V20 00.15 Cerium oxide (0602).... 05.(] Manganese oxide (MnO;) ()1. 4 Nickel oxide (Ni203) 0-0. 01 Cobalt oxide (000)... 0-0. 003 Copper oxide 0-0. 4 Silver oxide 0-0. 3

To the batch ingredients are added suitable fining agents such as antimony oxide, arsenic oxide, or sodium-chloride in an amount ranging approximately from .5% to 2%, and the oxides of vanadium, cerium, titanium, manganese, nickel, cobalt, copper and silver are included for controlling the resultant color and ultra-violet absorbing characteristics.

In preparing batches for producing glasses in accordance with this invention, it has been found that the silica content should be provided in amounts ranging between 60% and 72% since when using more than 72% the melt will tend to be viscous while less than 60% will result in a glass which is not chemically durable.

The boric oxide is used to help in the melting by making the glass a little more fluid and tending to improve the chemical durability. However, it should be held to not more than 7% agezcpoe 5; since larger amounts produce undesirable characteristics in the glass.

Soda and potash are included in amounts ranging approximately from 14% to 20%, .part as carbonate and part as nitrate, althoughonly one or the other may be used, if desired However, such an alkali should be controlled in accordance with the amount of boric oxide used; that is, the boric oxide should be low or not used at all with a high alkali content,,but put ting in boric oxide and decreasing the alkali gives better chemical durability.

In instances when the boric oxide is-decreased' or removed, it is directly replacedby the silica of the batch. This, therefore, will increase the silica content upwardly to theupperlimitsgiven. in Table A.

The total lime, titaniaand lead oxide contents should be held to approximately between:9 and, 11%. However, the lead oxide may be substituted in whole for the lime if desired; also, lime can be used without any lead oxide. Combining lime with lead oxide improves the chemical stability of the glass. The titania can be substituted for lime or lead oxide but should-not be used in excess of 5%.

However, since the lead oxide content. is re.- sponsible for producing the desiredX-rayabsorption, it is necessary to include it in amounts of at least 3% PhD whereupon the resultant. glass will absorb substantially all theX-rays generated by voltages up to 40,000 volt electrons. This is sufiicient absorption for present purposes since it is believed that the present invention will generally be used with lower electron voltagessuch as the conventional television kinescope tubes which generate a maximum of approximately 36,000 volt electrons.

The oxides of manganese, nickel, cobalt, vanadium, cerium, titania, and copper, together control the transmission in thevisible portion of the spectrum and the amounts used must be carefully controlled. The vanadium oxide, or cerium oxide, or titania and/or copper oxide or combinations thereof. should be provided in an amount in accordance with the ultra-violet absorption desired. Then the manganese oxide, or nickel oxide, or cobalt oxide, or combinations thereof are added to get a substantially neutral colored glass. Since it has been-found that manganese oxide, when used in substantially large. quantities, willproduce a glass having a transmission curve exhibiting a marked dip in the center on yellow-green region, it is preferable to provide the manganese oxide in greater quantities than the vanadium oxide to get the desired halance anii produce a glass having the desired transmission curve. The manganese oxide may be varied .approximately from? 4 to 12 times the amount of vanadium oxide depending upon the transmissionv desired. and. the thickness of the glass to be produced and. is included in amounts The. vanadium content will be within the-range-of rangin from approximately 0.5 to 1.4%,

.from approximately 0.051to 0.15%.

of the spectrum. It has also been found. that. additions. to the batch mixture of silver oxide reduces the-ultra-violet transmission with substantially little if any effect upon the visible spectrum; Copper oxide can be" included inamounts ranging approximately from 0fto0.4 andysilver-oxide approximately from 0 to 03%. Large amounts of'coppenoxide will cause high:

points to exist in the blue-green portion of the:

spectrum which may be corrected by reduction of vanadium oxide in the batch mixture, the reduction being proportionate tothe amount of vanadium oxide in the batch: asthe amount of;

increase in-the copper oxide is proportionate to the total amount ofcoppereoxide:inlthe:batch..

If cerium oxide replaces vanadium oxide in part or entirely, it will increase-the transmission in'the' green-yellow-red portion of the spectrum. compensated for by the addition of copper oxide or cobalt oxide, or. both, in amounts. controlled so as to substantially'restore theneutral appeahance of the resultantglass.

If the manganese oxide is replaced partially or entirely by cobalt oxide, the-vanadium oxide present in theglasswillcause theresultant glass to still have a neutral appearance becausethe. vanadium oxide tends to'a-bsorb or oompensate' for the blue introduced by the'cobalt-oxide.

If nickel oxide is introduced either entirely or partially for cobalt oxide or manganese oxide, the; nickel oxide has the effect of compensating for the green maximum transmission of the vanadium oxide with the resultant glass therefore having a neutral appearance.

The titania has little, if. any,.efiect' upon-the visible appearance of the glassbut does cause the. ultra-violet absorption. limit to move in toward the visible.

The following Table..-B.lists several difi'erent batch mixtures which may be used to form satisfactory glasses in accordance with this invention':

TablcB:

Amounts in percent Ingredients Batch A Batch-O" Batch E Batch'F Batch G Silica (SiOQ) Boric oxide (B20 Soda (N310). Potash (KzO)-;. Lime (CaO). Lead oxide (PbO) Antimony oxide (Sb O Manganese oxide (MIlOz) Vanadium oxide (V205)... Arsenic oxide (AS203) Copper oxide (CuO) "Silver oxide AgzO) eeeepre r pez' peppr-rwrws e germ-ses m This. increase in transmission may" be" Table Amounts in percent Batch V Y 7 4fl9 7 7 3 o Ld0L000 h 6 c t a B X x 3 h 400000 51 m c .M 4m773010000 0 B 21 W 300000 -D1O h 11 1 a B 5 W5 200000 5 02 00 L40 .7 7 &01 0&0 0 0 6 1 Table B-Continued nu 64w77311000 8 N m0000056m 0 0 U 900000 5 05 0 4m773]0000 w4m7 301030000 t t B a B B 000 T A 5 w wmmmm 338 w W 6 310000. N MA 7301030 00 a B B L 2 850 3 M 5 dammed. .588 .1. o m 6 m m WLMZZSOI 0 00 a n B m B a 2 8.0 5 K t nn p R 0 as w 6 A0 7 7 3 10 000 .m m 400000 51 0 0 m 6 1 m mammlaor 000 B m B o 5 U %0000056%00 m Q 5 2 NW4 0 mimmzatceeo. a h wer M M m4m77301 00 B B I 0000054Mm% P m m memzlaLrdae m 400000 51 00 a M &w 7 7 3 01000 0 B B H 5 00 O 8 8 0 5 h 20000052110 D 400000 50 0 0 c c M M B B Ingredients Ingredients Silica (SiO2)..

(MnO Nickel oxide (Niz 03) Boric oxide (B203)-.. Soda (N320).

Potash (K) Lead oxide (PbO) Titania (TiOz). Antimony oxide (Sb 0a). Vanadium oxide (V10 Cerium oxide (OeOz).. Manganese oxide Cobalt oxide (00 O) Ingredients Copperoxide (CuO)- Copper oxide (CuO) Glasses produced from the above formulae have outstanding characteristics with respect. to

all the practical criteria, the chemical durability is good, and the glasses have a desirable coefiicient of expansion which renders them readily fusible with other stable glasses or with the metal of cone-shaped walls 4.

In producing glasses from the above batch B0110 mixes, the melting can be done in a, relatively short time at temperatures ranging between 2600 to 2775 F. or the temperatures can be dropped by 50 to 100 F. and the batches melted for a length of time ranging from 6 to 2 hours. 30

It will be noted, however, that the batches are melted under oxidizing conditions in any conventional induction electric, gas-fired, or other type of furnace.

It will be noted that Table C includes some alumina and iron impurities which are believed to be derived largely from attack of the melting crucibles.

Visual transmission characteristics of some of the glasses are illustrated in Fig. 5. The curve The resultant glasses were produced by melting the batches A through D at temperatures held between 2635-2700 F. for 1%; hours, and batch E at temperatures held between 2600-2700" F. for 1 hour 35 min., with the balance of the time schedule being used for fining and for reducing 7 the temperature to working range.

Table C which follows gives the approximate indicated by numeral 9 illustrates the visual chemical analyses of glasses produced from the transmission of the glass of batch A, curve 10 of batches represented by batch B, batch N, batch batch B, curve H of batch C, curve l2 of batch Q, and batch T respectively in Table B: u D. and curve I30; batch E.

Batches Fit-through Yuwere melted at corresponding timectemperatureacycles- The-.curve indicated. by {numeral .25 -in .Fig.: 6 indicates the resultantwisible. transmissioncurve ofjthe glass 10: screen .ofhthe'tube... The color. .can. be defined. .as green. ..or. -greenishcblue, and .is decidedly advanctageous since. it will... aid.- .in increasing. contrast discrimination inthe ima e .bydecreasing vglare of batch-F. numeral 2! of batch G, numeral 28 and..reducing.difiusion .of..the..light-.emanating of batch Handmumeral-Zdofbatch-I. In Fig.7 from.thetubeasitpassesthroughtheglass. The numeral 3 8 indicates: the? visible. transmission color issuch, however, thatit thaswsubistantially curve .ofitheglass produced frombatch J, numeral no. alteringeffect on. the .color .of. .theimage pro-.- 3] of batch-K, numeral.32-of batch L,. and nuduced by akinescope, whether. colored or. black mer-al-.,33;ofbatch.M. 10 andwhite only...

The transmissioncurves of.-glasses made ac= The present glassflstillgfurther.improvesupon cording; to batches N-through :Y. aresimilar to thepriorart by possessing the additional .Xcray thosecsetforth-above. absorptionfeature whichiresults. ingreater safety Itew-ill be notedthat thes-addition of. copper withrespect. to theperson ofandparticularthe oxide lowers the transmission slightly in the red visionof an-.0bserver... reg-ion of-the -visible spectrum While additions of The glass batch.formulas, transmission curves, silver-oxidecslightly lowers the curvein the ultraandpercentages .givenhereinbefore.aregby way violet regionofl the spectrum. of. .illustrationonlyand shouldnot be .limitive .of

The :ultra-violet transmission characteristics of the .inventionexcept .insofaras. they arespecieach --of theeglasses producedtby melting the ficallyrecited inst-he appended claims. batchese listed-inwTahle 3B:- areshownc. in the 1301- It. is..partic.u1arly pointed .outthat the. glasses lowing Table D: set forth inthe above .formulaewillhave a lineal TableD U-V Transmission in percent Wave Length. 7 I

Batch Batch. Batch. Batch. .Batch Batch Batch Batch Batch Batch" Batch Batch Batch A- B I o D E F e H' I J. K L; Mt.

45.0- 4821 31.9 13.0 37. 9 50.3 50.8- 03.2 58.9 01.8 51:8. 32.1 32.8 15.8 9.2 22.0 35.2 30.2 49.0 44.5, 47.2.. 35.5.5. 17.1. 10.4 3.7 2.8 8.3 18.8 20.2 31.0 20.8 4 29;2 1&0 5.0- 4.7 0.0 0.0 1.4 5.9 7.1 12.9 10.2 11.9 5.3. 0.7- 0.0 0.0 0.0 0.0 0.9 1.2 3.2 2.1 2.9 0.8. 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2' 00' 00 0.0"

U4V Transmission inpercent Wave-Lengthin Mu=- E Batch Batch; Batch: Batch Batch Batch Batch Batch Batch Batch. Batch. Batch N.:O P 1 a. T- U v" w x -Y' Since 'the:presently described: glasses are-in.- tended uprimarily' for;- use in; televisionwherein undesirable-z ultraevioleta radiationzzis :believed. to be::present;, theeultraeviolet absorption. charac teris-tics areuthereforecimportant.1. Researchwith respect-.to-tthe efieet ofzultrai-violetslight upon human eyes -haszindica-ted that rtheathreshold.;-of vision. of-r an -observerz'ofvz a: television ,I kinescope tubes is I lowered: the uitracviolet; radiation. Therefore; .by; makingzthee face portion; 3 of the tube oft atslass having! ultra-violet. absorption characteristics; in accordance Withu the." present teachings-,athis eliminatestthe possible effectv of ultra-violet 1 rad-iation'iupon; the observers eyes amt-results? in; maintenance-1 0i the threshold. of vision-pf the observerat .substantially the .normal leve1..w=hereby-.; the-observer is. able to-twatch the kinescopecwithv greater. ease; less-eye strain, and less-fatigue; The-absorbing glassmay; of course, be. efiiciently .used. as. a-iaminate l4 cemented. as at .15.or.otherwise. .superimposed upon the face portionlofthetube. as sho /min Rig. 3, or'may be. made-astasseparate. filter I it. supported by a suitable structure. I? between: theetube and the observer...

Thepresentglass further improves. upon the prior 9 art. by combining. with the. foregoing ad.- vantages. the. additionaladvantage. that .it is slightly colored fcr increasinacontrast. discrimination, intthe image produced. on, the fluorescent coeiiicientv of: expansion of 10.23 410? per .degree (3., from. 25?. whichis room. temperature, to substantially 500?- C., which. is approximately annealinstemperaturm This expansion simulates that of; the metals. used .iniormingthe jackets or casings. of...conventional .cathode; ray tubes and thereby more .readilyenables. the .face portions. 3 to be permanently.fusedinsealed relationwith the. side .walls .4 .of the jackets. or, casings of the tube..

The glassesproduced .by the. procedures outlined .above have .beenreferred toasbeing of a controlled c01or,.,or. morespecifically as. having a light green. or. greenish-.blnecolor. Although to. a scientist, a. comp1ete.specification of the colors .desired for .theg1asses. of. thissinvention canbe readiromthecurves shown in. Figs..5,-6 and..7,fin order .to better define. the color limits which are acceptable within the scope of'this invention and to. differentiate from prior art glasses of similar, types,.the colors may .,be-fur.- ther defined byusing the standard observer and coordinate system adopted in 1931.103 the Inter-.- national Commission. on Illumination. These specifications will all be givenin termsof the standard ICI. illuminant 0,, representative. of average daylight. of a. standard observer, and of a. standard thicknessof, .2.0 millimeters...

With reference to .Fi'g. 8 in. the accompanying drawings, there is given a. plotjcf the :nandy coordinates in the aforementioned color specification system and the color qualities derived from them, namely the. dominant wavelength and the purity of the color being described. The third attribute of color, brightness, as derived from Y, has been found to agree almost exactly with the physical property "visual transmission" previously discussed and quoted for specific glass compositions and limits. Therefore, as previously stated, for the purposes of this invention, this property of brightness can be varied between 48% and 82% according to the particular shade desired and independently of the other two attributes of dominant wavelength and purity.

Referring to Fig. 8, letters A and B indicate glasses produced respectively from batches A and B and indicate the colors of the two examples given hereinbefore. The dominant wavelength, it will be noted, is approximately 550 millimi- 'crons for both, being 551 mu for A and 548 mu for B, and the purity property is approximately 2%, being actually 2.2% for A and 1.9% for B.

However, batches C, D and E produced glasses having colors noted respectively by letters C, D and E in Fig. 8, which colors are also acceptable and well within the scope of this invention. Color E is near the 550 mu wavelength line and has a purity property of above 2 Colors C and D have dominant wavelengths of approximately 523 mu and 511 mu respectively and have approximate respective purity properties of 1.2% and 0.6%.

The above examples AE indicate several of the glasses on which the chromoticity values have been actually determined, but it is to be understood that many other glasses including the others described herein have been so produced which fall within the scope of this invention, such, for example, as the glasses of batches F--Y.

Although throughout the specification manganese oxide has been referred to as used in the various batch glasses as a means for controlling the curve throughout the visible spectrum, it is to be understood that manganese oxide may be partially or completely replaced by cobalt oxide. In instances when the cobalt oxide is used to replace the manganese oxide, a much lower percentage of the cobalt oxide with a maximum of about .003. It is pointed out that cobalt oxide is a much more powerful colorant than manganese oxide and, therefore, larger amounts of manganese oxide are required in order to obtain substantially the same comparable results.

A cathode ray tube having a transparent face portion 3 made of a glass formed in accordance with these teachings may befurther improved as to contrast discrimination of the image produced on the fluorescent screen I by providing means for reducing halation caused ,by reflections of light rays from the surfacesof the glass onto the fluorescent screen. Such meansmay be in the form of the reflection reduction coatings 5 and 8 provided on the opposed surfaces of the face portion 3. The outer coating 6 may be in the form of any suitable material characterized by its ability to increase the transmission and reduce the reflection of light rays passing through the face portion 3.

Thus, with reference to Fig. 2, when a particle,- for example, of the material forming the fluorescent screen 1, which particle is diagrammatically indicated at I8, is caused to fiuoresce by bombardment of the electron beam E, light rays l9 which pass therefrom into the glass 3 will emerge from the outer surface of the glass substantially unaltered except for the absorption thereof by the glass itself. Light rays 20 which are emitted by the particle I8 and which strike the outer surface of the glass at angles less than the critical angle, indicated by line 2|, will be partially refiected back through the glass toward the fluorescent screen 1 as indicated by numeral 22. These reflections 22 will, if of suificient brightness, cause illumination of other particles 23 of the fluorescent screen and thus cause what is known as halation. However, in accordance with this invention, the absorptive characteristics of the glass plus the low reflection characteristics of the coating 6 will greatly decrease halation. I

The inner reflection reduction coating 8 may also be of any suitable type but is preferably formed of a myriad of sub-microscopic, discrete, micro-granular transparent solid particles which form minute projecting irregularities on the glass surface, the concentration of the particles in the irregularities decreasing from the surface of the glass outwardly, and the material of the particles being such that the effective index of refraction of the coating varies from substantially unity at the coating-fluorescent material interface to an index value which progressively increases as it approaches the glass until it substantially approximates the index of refraction of the glass, the total thickness of the coating being preferably of the order of one-quarter wavelength. Such a coating 8, due to the extremely small size of its particles and irregularities compared to the relatively large size of the particles of the fluorescent screen 1, will cause the screen 7 to be spaced from and consequently out of optical contact with the glass 3. Thus,-the reflections 22 will be still further prevented from illuminating the screen 1. I, u

The outer coating 6 also aids in providing comfortable viewing of the cathode ray tube by an observer by reducing reflection into an observers eyes of light rays emanating from sources outside the tube.

Since light rays 24, which emanate from the particle l8 and strike the surfaces of the glass at angles greater than the critical angle will continue on through the glass without emerging, it is further desirable to provide means on the outer periphery of the face portion 3 for rendering the rays 24 ineffective. Such means may be in the form of a highly polished surface for permitting the rays 24 to escape substantially without diffusion, or in the form of a coating 25 of light ab sorptive material for absorbing the rays 24. Such an absorptive coating may be a suspension of graphite particles in oil or cement such as Canada balsam, or black lacquer, which coating should possess an index of refraction equalto or higher than the index of refraction of the glass.

From the foregoing teachings, a glass which is particularly desirable for use with television kinescopes or other cathode ray tubes can be produced with controlled visual transmission characteristics, color, and'ultra-violet and X-ray absorption characteristics by combining controlled amounts of the oxides of manganese, vanadium, silver and copper together with lead oxide, in a base crown glass batch and melting under oxidizing conditions within the temperature ranges and time cycles given herein. The resultant glass will, when used in connection with cathode ray tubes, increase contrast discrimination [of ,the image produced on the screen of the tube, absorb ultra-violet radiation and thereby maintain the 13 threshold-d vision. ofanobserverat substantially normal level, absorb harmfulv X rays; and transmit substantially truecolor; and; when: used with reflection reductionsurface coatings, with or withouttperipheral light "eliminating means, will greatly reduce halationand thus-further increase contrast discrimination the image: Although the above glasses are dscribed as being particula'rly desirable for use intelevisi'onp it is to be understood that any other use thereof is within the scope -of "the present invention- From the-foregoing; it will be seen that wehave produced means I and methodsof a simple and eflioient- -nature for" producing all ofthe objects and advantages of the present invention.

It will be understood; however; that many changes maybe made in-the compositions,- structures and methods shown-and described without departing from the .spirit of' the invention as expressed intheaccompanying claims; and" it is; therefore; not desired that the-compositions; structuresand' methods-described"be li'mitive-of the-invention since th'e preierred only' have been given byway of- 'ill'ustration.-

We-claim:

1. A glasscihaving controlled"ultra -violet ab sorption; characteristics and whbse-- chemical analysis-may beexpressed substantially asiollows:

Approximate Ingredient Percentage Silicon :dioxid'eisioi)L Mm. 67; 6 Aluminum oxide plus. iron oxide. (RzOa)... 1.02 Calcium oxide (0210) 7. 05 Lead oxide? (PbO). 3. 23 Sodium oxidev (Nag 8.70 Potassium oxide (KiO 6.43 Borio oxide (B20 ),v ..s. 3.60 Antimony trioxile (sbaQaL-m 1.65 Manganese'dioxide- (Mn'Og). 59 Copperoxide-(CuO) 3 .07 Vanadium oxide. (VzQa) 08 2. A glass .having controlled u1tra-violet...ab-. sorption.. characteristics. and. whose chemical analysis v.may be expressed. substantially as. fol.-

lows

. Approxim ate. Ingredient Percentage Silicon dioxide (S102) v.

Aluminum oxide plus iron oxide (RiG 56 Calcium oxide (GaO) 6. 79 Lead oxide (PbO) 4.47 So'diilm oxide (Na'aO) 8.68' Potassium oxide (K 6. 74 Boric oxide (B 3. 96 Antimony tiiOXilG (SbaO 1.60 Cobalt oxide 000).. 0006 Nickel oxiie (NizOi). 009" Copper oxide (CuO) E; Vanadium oxide (V205)-.. .10.,

- 3.. A. glass. having; controlled ultraeviolet ab..-. sorption characteristics. and. whose. chemical analysis, may be expressed: substantially as .fOl-I lows 4 An: Xx-ray: and-"ultraeviolet absorbing: glass suitable .foruse as a .cathodesrayttube face, filter andethe :like consistingzof the :ifused :product we suiting fromabatch mixsicomprising 'fromiabout 14-to 20 %1.alkalioxideaafzom. about 60 to1i'72% silica, fromabout .3 to-.1.l%;lead;oxide, an amount ranging approximately, from; zero. to: about .a 11%. of copper. oxide 1 andiultraeviolett. absorbing; oxide from a the group consisting: of. vanadium-r oxide; cerium oxide; and mixtureszthereof 1' andrcoloring oxide from: theigroup' consisting of:manganese oxide,- nickel oxide, cobalt oxide and :mixtures thereof in suohramounts as withtheicopper oxide to produce .a; substantially neutral colored ultra: violet absorbing glasstshaving its dominant w wave length: near *thecmiddle :of the visible spectrum with a.- brightness "propertyfbetween' about48 and 82'%-and.ja purity property of roughly. 2%, the vanadium: oxide-when containedinithe glass not exceedingabout: .15 ,1 .theicerium oxide '5 the manganese oxide 1.4%; the nickel: oxide :01 %i and the cobalt oxide-.OOB-efln 5.: An X.-iray anci'fultra violet absorbingglass suitable for use as ascathode ray tube :face'; filter and the-likev consisting. .ofsthe fusedcproduct :re sulting from; a; batch. mixcomprising' from; 14 'to 201% alkali oxides, from .about:60..to= 721% silica. from-about 9;to 11% of-a mixture 'offleacl -oxide titania and lime, theeleads oxide; embodying at least 3% of the glass andi.-the'-titania.'beingnone tain'ed an amount not. exceedingyabout 5%,. said: glass (further containing anwamount: rang-.- ing approximately: from a zero :to about .4%.-:- of copper: oxide and amounts of? ultra violet abasorbing oxidefromrtthe,grouptconsisting of vana:-. dium oxide, cerium oxidez-an'drlmixturesithere! of and: a .coloringxoxidea-from- ;.the;:group consisting: 'of imanganesei oxide, nickel .oxide, cobalt ox-. ide and mixtures thereofsuch1asrto.produce-ze ith the =copper-roxide ai.-'substantially: neutral. colored ultra-violet absorbingglasshavingsits dominant wavelength near; the:m-iddle 0f-:the :visible spectrumwith .a-i brightness: propertyybetween; about 48'and 82% and-"a puritygpropertyiof roughly 2%;

the vanadium;oxide'zwhenzcontainedfinwthee glass not exceeding about .15.%,. the :ceriumroxide 5%, the manganese-oxide 1.4 .the nickel oxide .01 and the:cobalt 'oxide; .0u3

6. An ultra violet .andzXeraya absorbing glass of substantially neutral. ;color:.- comprised essen-; tially. of a.fusedmixture i-of' silica,.-. soda, potash and: lime in amounts. sufiicient :.to:form. a sub.= stantially. homogeneous; glass: and further con taining fromr.about-.r3..-tos.11% of leadoxide, an amount ranging approximately 1: from zero to about .4%- ofscopperr oxide, ultra-violet absorbe ingoxidefrom-the-group consisting of-.ivanad'rum oxide, cerium .oxidesandzmixtures; thereof," the vanadium; oxide when-=1 contained in; the: glass;

. notuexceeding.;.15% and the cerium oxide; not exceeding 5%, colorant from the group cone sisting tofemanganeseioxide, nickel oxide, cobalt oxide and mixtures ztliereoi, and-the manganese oxide when contained vin the glass not exceede ing 1.4% the .cobalt oxidernot exceeding--003% and the :niokelioxideenotexceeding-1.01%, said colorant. and: ultra-violet absorbingr oxide to-. gether with the copperoxide providing said; glass for athic'kness, of approximately-:6 millimeters with a-"transmissi'onr of from 1 to 170% at: 400 millimicrons; 58 'tor'1'6=%" atr500 rni'liiinicrons, toc'il at fiuoamillimicrons, 67' to at 700 millimicrons-an'd 'le'ss than- 13% forradiations shorter than 360 .millimi'c'rons:

'7." u1tra=violet and- X ray-absorbirrg' glass of substantially neutral color comprised essentially of a fused mixture of silica, soda, potash and lime in amounts sufficient to form a substantially homogeneous glass and further containing from 3 to 11% of lead oxide for absorbing X-rays, an amount ranging approximately from zero to .4% of copper oxide, metallic oxide from the group consisting of vanadium oxide, cerium oxide and mixtures thereof, the vanadium oxide when contained in the glass, not exceeding .15% and the cerium oxide not exceeding 5%, said copper oxide and metallic oxide absorbing ultra-violet radiations and normally introducing color to *the glass, said glass further containing other ultra violet absorbing ingredients from the group consisting of titania, silver oxide and mixtures thereof, the titania when contained in the glass not exceeding about 5% and the silver oxide .3 and colorant from the group consisting of manganese oxide, nickel oxide, cobalt oxide, and mixtures thereof such as to substantially compensate for said color introduced by the ultra-violet absorbing oxide from said group, and the manganese oxide when contained in the glass not exceeding 1.4%, the cobalt oxide not exceeding .003% and the nickel oxide not exceeding .01 said colorant and ultra-violet absorbing oxide with the copper oxide and other ultra-violet absorbing ingredient together providing said glass for a thickness of approximately 6 millimeters with a transmission of from 45 to 70% at 400 millimicrons, 58 to 76% at 500 millimicrons, 50 to 71% at 600 millimicrons, 67 to 80% at 700 millimicrons and less than 13% for radiations shorter than 360 millimicrons.

8. A glass having controlled ultra-violet and X-ray absorption characteristics and of a controlled substantially neutral color, said glass being made from a batch mix comprising from about 60 to 72% silica, from about 14 to 20% alkali, and having incorporated therein the oxides of vanadium, manganese, copper, silver and lead for producing the desired color and absorption characteristics, the vanadium oxide comprising from about ,05 to about .15 the man-' ganese oxide from about .5 to about 1.4%, the copper oxide in an amount ranging approximately from Zero to about .4%, the silver oxide in an amount ranging approximately from zero to about .3% and the lead oxide comprising from about 3 to 11%, said glass having transmission characteristics for a thickness of approximately 6 millimeters which permits transmission of less than 13% of ultra-violet at 360 millimicrons in the spectrum and visual transmission of approximately from 45 to 70% at 400 millimicrons, 52 to 76% at 500 mu, 50 to 70% at 600 mu, and 66 to 80% at 700 mu, with an average white of approximately from 60 to 70%. I

9. A glass having controlled ultra vio'letend X-ray absorption characteristics and of a controlled substantially neutral color, said glass being made from a batch mix comprising from about 60 to 72% silica, from about 14 to 20% alkali oxide and having incorporated therein controlled amounts of the oxides of vanadium, manganese, copper and lead for producing the desired color and absorption characteristics with the manganese oxide being used in an amount greater than the vanadium oxide, and the lead oxide being contained in an amount from 3 to 11%, the vanadium oxide from..05 to .15 the manganese oxide from .5 to 1.4% and the copper '16 oxide in an amount ranging approximatelyfrom zero to about 4%, said glass for a thickness of approximately 6 millimeters having substantially no transmission of ultra-violet below approximately 340 millimicrons in the spectrum and visual transmission of approximately from 45 to'65% at 400 millimicrons, 62 to 72% at 500 mu, 59 to 69% at 600 mu, and 75 to at 700 mu, with an average white of approximately from 60 to 70%.

10. A glass having controlled ultra-violet and X-ray absorption characteristics and of a controlled substantially neutral color, said glass being made from a batch mix having incorporated therein approximately from 60 to 72% of silica, approximately from 14 to 20% of alkali oxides, from about 3 to 11% of lead oxide, approximately 0.5 to 2.0% of fining agents, and the oxides of manganese, vanadium, copper and silver in amounts controlled in accordance with the transmission and color characteristics desired of the resultant glass,'the vanadium oxide comprising from about .05 to about 15%, the copper oxide in an amount ranging approximately from zero to .4% and the silver oxide in an amount approximately from zero to 3%, with the manganese oxide being in amounts ranging approximately from 4 to 12 times the amount of vanadium oxide, said glass for a thickness 01' approximately 6 millimeters having substantially no transmission of ultra-violet below approximately 340 millimicrons in the spectrum and visual transmission of approximately from 45 to 70% at 400 millimicrons, 56 to 76% at 500 mu, 50 to 70% at 600 mu, and 66 to 80% at-700 mu, with an average white of approximately from 6 0 to 70%, and substantially no transmission of X-rays generated by 40,000 volt electrons.

11. An X-ray and ultra-violet absorbing glass of substantially neutral color consisting of the fused product resulting from a batch mix comprisin from 14 to 20% alkali oxides, from about 60 to 72% silica, from about 3 to 11% lead oxide, ultra-violet absorbing oxides embodying a mixture of copper oxide and oxide from the group consisting of vanadium oxide, cerium oxide and mixtures thereof, said oxides having a coloring effect in the glass, and a sufficient amount of oxide selected from the group consisting of manganese oxide, nickel oxide, cobalt oxide and mixtures thereof as to control said coloring effect and with the copper oxide and other ultra-violet absorbing oxide to produce for said glass transmission characteristics for a thickness of approximately 6 millimeters of from 45 to 70% at 400 millimicrons, 58 to 76% at 500 millimicrons, 50 to 71% at 600 millimicrons, 67 to 80% at 700 millimicrons, less than 13% for radiations shorter than 360 millimicrons, and wherein when contained in the glass, the vanadium oxide content does not exceed about-.15 the cerium oxide content about 5.0%, the man'ganese oxide, about 1.4%, the nickel oxide about 01%, and the cobalt oxide about 003%, the copper oxide comprising an amount ranging approximately from zero to about .4%.

12. An ultra-violet absorbing glass of substantially neutral color consisting of the fused product resulting from a batch mix comprising from 14 to 20% alkali oxides, from about 60 to 72% silica, from about 9 to 11% lime, an amount ranging approximately irom zero to 4% of copper oxide and an amount of ultra-violet absorbing oxide from the group consisting of vanadium oxide, cerium oxide and mixtures thereof, together with an amount of coloring oxide from the group consisting of manganese oxide, nickel oxide, cobalt oxide and mixture thereof such as to produce with the copper oxide transmission characteristics for a thickness of about 6 millimeters of said glass of from 45 to 70% at 400 millimicrons, 58 to 76% at 500 millimiorons, 50 to 71 at 600 millimicrons, 67 to 80% at 700 millimicrons and less than 13% for radiations shorter than 360 millimicrons and wherein when contained in the glass, the vanadium oxide content does not exceed about .15%, the cerium oxide content does not exceed about 5.0%, the manganese oxide does not exceed about 1.4%, the nickel oxide does not exceed about .01%, and the cobalt oxide does not exceed about 003%, said glass further containing silver oxide and in an amount which does not exceed about .3%.

13. An ultra-violet absorbing glass ofsubstantially neutral color consisting of the fused product resulting from a batch mix comprising from 14 to 20% alkali oxides, from about 60 to 72% silica, from about 9 to 11% of lime and titania, with the titam'a being contained in an amount not exceeding about of the whole, an amount ranging approximately from zero to .4% of copper oxide and an amount of ultra-violet absorbing oxide from the group consisting of vanadium oxide, cerium oxide and mixtures thereof, together with an amount of coloring oxide from the group consisting of manganese oxide, nickel oxide, cobalt oxide and mixtures thereof such as to produce with the copper oxide transmission characteristics for a thickness of about 6 millimeter of said glass of from 45 to 70% at 400 millimicrons, 58 to 76% V the nickel oxide does not exceed about .01%, and the cobalt oxide does not exceed about 003%.

14. An X-ray and ultra-violet absorbing glass consisting of the fused product resulting from a batch mix comprising from 14 to 20% alkali oxides, from about to 72% silica, from about 9 to 11% of lime and lead oxide, the lead oxide embodying at least 3% of the Whole, an amount ranging approximately from zero to about .4% of copper oxide and amounts of ultra-violet absorbing material from the group consisting of vanadium oxide, cerium oxide and mixtures thereof and selective visible light absorbing material fom the group consisting of manganese oxide, nickel oxide, cobalt oxide and mixtures thereof as to produce with the copper oxide a substantially neutral colored glass having its dominant wave length near the middle of the visible spectrum with a brightness property between about 48 and 82% and a purity property of roughly 2 and when contained in the glass the vanadium oxide not. exceeding about .15%, the cerium oxide 5%, the manganese oxide 1.4%, the nickel oxide .01% and the cobalt oxide .003%, said glass further containing an amount of silver oxide from near zero to .3%.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 667,646 Bergier Feb. 5, 1901 1,292,148 Taylor Jan. 21, 1919 1,726,635 Taylor Sept. 3, 1929 2,143,022 McClure Jan. 10, 1939 2,219,122 Weidert et a1. Oct. 22, 1940 2,282,601 Blau May 12, 1942 2,582,453 Pincus Jan. 15, 1952 FOREIGN PATENTS Number Country Date 11,019 Great Britain 1888 

12. AN ULTRA-VIOLET ABSORBING GLASS OF SUBSTANTIALLY NEUTRAL COLOR CONSISTING OF THE FUSED PRODUCT RESULTING FROM A BATCH MIX COMPRISING FROM 14 TO 20% ALKALI OXIDES, FROM ABOUT 60 TO 72% SILICA, FROM ABOUT 9 TO 11% LIME, AN AMOUNT RANGING APPROXIMATELY FROM ZERO TO .4% OF COPPER OXIDE AND AN AMOUNT OF ULTRA-VIOLET ABSORBING OXIDE FROM THE GROUP CONSISTING OF VANADIUM OXIDE, CERIUM OXIDE AND MIXTURES THEREOF, TOGETHER WITH AN AMOUNT OF COLORING OXIDE FROM THE GROUP CONSISTING OF MANGANESE OXIDE, NICKEL OXIDE, COBALT OXIDE AND MIXTURES THEROF SUCH AS TO PRODUCE WITH THE COPPER OXIDE TRANSMISSION CHARACTERISTICS FOR A THICKNESS OF ABOUT 6 MILLIMETERS OF SAID GLASS OF FROM 45 TO 70% AT 400 MILLIMICRONS 58 TO 76% AT 500 MILLIMICRONS, 50 TO 70% AT 600 MILLIMICRONS, 67 TO 80% AT 700 MILLIMICRONS AND LESS THAN 13% 